The present invention relates to sperm fertility and in particular to prediction of fertility from DNA staining.
Semen quality examinations are a central role of the semen-processing laboratory. Many semen quality exams exist to evaluate semen. However these tests are often flawed because they are designed to find higher- rather than lower-fertility males, or the approaches reward extreme values rather than those that pass a minimum threshold (Parrish et al., 1998; 2006). In addition, fertility of bulls used in commercial artificial insemination of dairy cattle is likely most dependent on non-compensable semen traits, i.e. traits that cannot be overcome by increasing the number of sperm inseminated. Many semen quality exams, however, target the evaluation of compensable semen traits such as the percentage of motile, live or acrosome-intact sperm.
Research has been directed to potential non-compensable defects in sperm of lower-fertility bulls that alter events during the first cell cycle of the zygote and result in changes to the timing of cell divisions and success of embryo development (Eid et al., 1994; Parrish and Eid, 1994; Parrish et al., 2006). It has been determined that defects or damage in sperm DNA are responsible for these effects. Since a significant portion of the sperm nucleus consists of DNA, it has been hypothesized that subtle changes in sperm DNA might be reflected in physical properties such as sperm nuclear shape. As a result of research in this area, it has been demonstrated that careful measurements of sperm head morphology can be used to predict fertility (Parrish et al., 1998, 2006, 2012). Nevertheless, there is an ongoing need for additional methods to assess fertility.